The present invention generally relates to mobile communication systems and particularly establishing data calls employing different data rates and bearer services.
In addition to conventional speech transfer, modern mobile communication systems provide their users with various kinds of data transfer features. The services provided by the mobile communication systems may generally be divided into Tele Services and Bearer Services. A bearer service is a telecommunication service which constitutes the transfer of signals between the user-network interfaces. As an example of bearer services, modem services are mentioned. In a tele service, the networks also provides terminal equipment services. Examples of major tele services, in turn, include speech, telefax, and videotext services.
The bearer services are usually classified into groups, such as asynchronous and synchronous bearer services, according to a characteristic feature. In an asynchronous bearer service, the transmitting and receiving data terminals only maintain their synchronization during each individual character to be transferred. In a synchronous bearer service, the transmitting and receiving data terminals are synchronized during the entire data transmission. Within each of such groups there is group of bearer services, e.g. a transparent service and a non-transparent service. In a transparent service, the data to be transferred are unstructured, and the transmission errors will be corrected by using channel coding only. In a non-transparent service, the data to be transferred are structured into service data units, and transmission errors are corrected (in addition to channel coding) by using automatic requests for retransmission. In addition, each user data rate is presently an independent bearer service. Therefore, there will be a hugely increased number of different bearer services. For example, the single channel data services of the Pan-European digital mobile communication system GSM (Global System for Mobile Communication) now has 6 different asynchronous bearer services for the rates 300, 1200, 1200/75, 2400, 4800 and 9600 bit/s.
A mobile subscriber may typically be entitled to different kinds of tele and bearer services. He may, for example, have access to a speech service, telefax service and various kinds of data services that utilize bearer services. A mobile terminating or originating call may therefore require any of the aforementioned tele and bearer services, or combinations thereof, for which reason the correct service must be addressed to the mobile communication network. In the GSM mobile communication system, for example, call set-up signalling transmitted by a mobile station contains information on the required service in a specific BCIE (Bearer Capability Information Element). The mobile communication network may thus choose the appropriate service for the mobile originating calls. Calls originating from an ISDN (Integrated Services Digital Network) also contain a similar information element, indicative of the required service. If, however, the call originates -from or is routed via the public switched telephone network (PSTN), information on the service type of the call will not be transmitted to the mobile communication network. In such a case, the mobile communication network should be informed in some other way what type of a basic service is required by the call. A prior art solution to the problem is represented by a Multi Numbering Scheme in which a mobile subscriber has as many directory numbers as he has different services to which he wishes to receive incoming calls. In accordance with the multinumbering scheme, a calling subscriber dials the directory number of the mobile subscriber according to the desired service. In the GSM system, the services of the subscribers are determined in a subscriber""s home location register (HLR), in which other subscriber information is also stored permanently. The HLR is also used for storing information on the mapping between the directory numbers and the services of the subscribers. In the HLR, a specific BCIE element indicating the type of a call and the network resources required for the call is also linked with the directory number (MSISDN).
For the network operator and the mobile subscribers, such a vast number of services causes confusion and trouble. In order for the mobile subscriber to be able to carry out data calls to applications of different rates, he must subscribe to several bearer services from the network operator. From the point of view of the network operator, it is in turn problematic that each user should require numerous directory numbers, which wastes the number space of the network. Furthermore, determining the services in the network databases consumes database capacity.
In the GSM network, for example, the problem is becoming more acute as the determining of high-rate HSCSD (High Speed Circuit Switched Data) data services, which employ multi-slot technique, increases the number of bearer services on top of the single-slot services already determined. Hence, it would be advantageous to both the network operators and the mobile subscribers if the number of different kinds of bearer services could be reduced.
It is object of the present invention to provide a digital mobile communication network in which one determined bearer service can handle as many data rates as possible.
This object is obtained by a method of the invention for establishing a data call in a mobile communication system. The method is characterized by the steps of determining for a mobile subscriber at least one data call bearer service covering several user data rates,
carrying out, upon establishing the data call between the mobile communication network and the mobile station, a user data rate negotiation for setting the user data rate to be used in the data transfer between the mobile station and the mobile communication network,
allocating radio channel resources for the data call according to the user data rate negotiated,
continuing call set-up to the second party of the data call.
The invention further relates to a digital mobile communication system which is characterized by comprising
at least one data call bearer service which covers several user data rates and which is determined for the mobile subscriber at the subscriber database of the mobile communication network,
a negotiation procedure between the mobile station and the mobile communication network, for negotiating during call set-up, a user data rate used in the data call for data transfer between the mobile station and the mobile communication network,
call control, allocating radio channel resources according to said negotiated user data rate.
The number of bearer services required in a mobile communication network can be significantly reduced by the method of the invention by determining a bearer service to cover several or all the user data rates, and by negotiating between the mobile station and the mobile communication network, at the call set-up stage, the data rate to be employed by the data call in the bearer service. The next step is to determine the data rate between the mobile communication network and the fixed network, such as the PSTN or ISDN, i.e. the data rate of the second party in the data call. If required, the data rate of the mobile communication network and the channel resources of the radio path are then adapted to the data rate used in the direction towards the fixed network.
At the initial stage of call set-up, a negotiation on the user data rate takes place between the mobile station and the mobile communication network at the call set-up stage. The mobile communication network may consequently limit the call to employ such a data rate which it is able to support, by signalling a rate parameter in the BCIE at the call set-up stage. The mobile station and/or an application used in a data terminal equipment connected thereto may also limit the call to use a transfer rate it supports by signalling a similar rate parameter in the BCIE. The mobile subscriber can also limit the call to use a desired data rate by configuring the BCIE rate parameter via the user interface. Following this, the mobile communication network allocates the radio channel resources and the network adaptor the call desires, and establishes a connection to the fixed network.
At the next stage, the data rate between the mobile communication network and the fixed network is negotiated or identified. If the call is a modem call, the network adaptor allocated above is a data modem. In the invention, the network adaptor modem may, within the specific data rate limit, carry out a data rate handshaking with a fixed network data modem employing any data rate. This enables operation with applications of the fixed network that use different rates. Said rate limit means that the handshaken data rate is to be limited to a level lower than or equalling the data rate negotiated by the mobile station and the mobile communication network at the first stage. As soon as the data rate handshaking has been completed, the network adaptor modem informs of the data rate negotiated in the handshaking.
If the information is Unrestricted Digital Information (UDI) towards the ISDN network, the data rate employed towards the fixed network is recognized either from the traffic channel itself, ISDN signalling, or in any other suitable manner.
At the third stage of the call set-up procedure according to the invention, the data rate of the mobile communication network and the radio path channel resources, allocated at the first stage, are if need be adapted to the data rate used by the fixed network and handshaken or recognized at the second stage. If the handshaken or recognized user data rate is higher than the rate negotiated by the mobile station and the mobile communication network at the first stage, the call is released in the case of a transparent data call. If the data rate handshaken or recognized at the second stage is lower than the transfer capacity of channel resources allocated on the radio path at the first stage, surplus capacity is released and/or channel coding is changed for a better one, if possible. If the data rate handshaken or recognized at the second phase is as high as the rate agreed upon at the first stage, the channel resources of the radio path are maintained unchanged.
The present invention enables significant reduction in the number of bearer services. It is possible to determine, e.g., one asynchronous bearer service which can be used in initiating all asynchronous data calls regardless of whether the call is terminated as transparent or non-transparent or which the final data rate will be after the call set-up according to the invention. This means that only one directory number, and a matching BCIE, has to be allocated for the subscriber for an asynchronous bearer service (compared to six numbers presently). This, in turn, results in a corresponding saving of database capacity and network number space. In addition, it facilitates making mobile-terminating calls particularly, because the calling subscriber only needs to know one asynchronous data service number. In the same manner it is possible to bring other, previously separate bearer services under one bearer service or service class for example so that all asynchronous data services constitute a bearer service, PAD access constitutes a bearer service, and Packet access constitutes a bearer service